We propose to determine the basis and consequences of the increased long chain polyunsaturated fatty acids (PUFA) found in Reye's syndrome (RS) sera. That this could be due to increased lipoprotein lipase (LPL), increased hepatic triglyceride lipase (HTGL) released into the plasma or increased phospholipase A activity (PLA1 or A2) will be tested by examination of serum and the cellular fractions of blood for these activities by using appropriately labeled substrates to distinguish these activities in the presence of appropriate activators and/or inhibitors. Adipose tissue LPL, heparin releasable and intracellular, will be measured in biopsied tissues from RS and controls. Tissues will be exposed to heparin to measure the releasable activity and intracellular LPL will be measured on the acetone ether treated residue. Also, the composition of membrane phospholipids will be determined and compared between RS and controls to seeif changes reflecting PLA2 action could account for altered membrane function seen in the acute disease. To explore the consequences of increased PUFA of activation of endogenous PLA2, isolated hepatocytes will be exposed to concentrations of PUFA of lysophosphoglycerides as seen in RS or to melittin to activate endogenous PLA2, examining the following: liver ornithine carbamyltransferase activity by conversion of 14C-carbamylphosphate to citrulline, liver lipid content including the CoA and carnitine esters and the ultrastructure by EM. Studies may be extended to the isolated, perfused intact rat liver if indicated. Abnormalities resulting may indicate their dependence on the membrane lesion resulting from melittin or, secondarily, on the resulting increase in PUFA released by increased PLA2 activation. Finally, the state of unsaturation of the fatty acid moieties of the adipose and liver lipids will be determined, emphasizing the non-triglyceride components but also including the triglycerides by classical extraction and separation procedures, identifying the fatty acid components by GLC-mass spectrometry. These studies would further our understanding of RS, placing into perspective the primary or secondary role of the FFA changes which have been reported.